Many people develop back pain during the course of their life due to traumatic injury, disease, or genetic defect. Typically, the patients' intervertebral discs, which support the spine, are damaged, causing the discs to bulge or herniate. The disc bulge then impinges on the nerves of the spine and causes back pain. Surgeons often perform a discectomy to trim the disc bulge to alleviate back pain. However, the discectomy may structurally weaken the disc and often leads to subsequent structural failure of the disc due to wear and aging, once again causing impingement on the nerves of the spine and back pain. Surgical implantation of a medical implant device to structurally support and separate the vertebrae may become desirable to end debilitating back pain and allow patients to regain normal life activities.
One known device for promoting fusion between adjacent vertebrae is an expandable interbody device (IBD). Such devices are generally configured to be inserted into the intervertebral space in a compact configuration, and then are expanded to an expanded configuration to restore the adjacent vertebrae to a desired spacing. Numerous mechanisms are known for expanding the height of an expandable IBD, such as a threaded screw which drives one or more wedge members against ramped surfaces to drive the outer surfaces of the IBD apart. (See e.g., U.S. Pat. No. 8,105,382). It is also known to provide an IBD with one or more openings in the top and bottom outer surfaces of the IBD for containing bone graft material to promote fusion between the vertebrae to stabilize the joint.
One disadvantage of known expandable IBDs is that the expansion mechanisms materially constrain or limit the area in which bone graft material may be contained. The expansion mechanisms often occupy the central part of the IBD, leaving little or no space for bone graft material. Further, it is difficult or impossible with known expandable IBDs to add bone graft material after the IBD is implanted between the vertebrae. While some expandable IBDs may be configured to hold bone graft material for promoting fusion, once the device is expanded, there may not be sufficient bone graft material to fill the bone graft cavity in the device such that sufficient bone graft material is kept in contact with the adjacent vertebral endplate to adequately promote bone ingrowth. In such cases, a safe and effective manner to insert additional bone graft material after insertion of the IBD into the intervertebral space is desirable.
Thus, it would be advantageous to provide an expandable interbody device for implantation in the intervertebral space between vertebral bodies for supporting and/or spacing apart the vertebral bodies and having improved characteristics for promoting bone growth and fusion therebetween and/or immobilization thereof. It would further be advantageous to provide a system for safely and effectively inserting bone graft material into the intervertebral device after the device has been inserted into the intervertebral space. The present invention may be used to provide these and other benefits, as will be apparent from the following description of embodiments of the present invention.